Experimental-Computational Investigation of Elastic Modulus of Ultra-High-Rise Pumping Concrete

Based on the ultra-high-rise pumping concrete engineering test with pumping height of 407 m and maximum pumping pressure of 19.3 MPa, the variation of elastic modulus of the pumping concrete was analyzed by experiments and computational method. Firstly, the back scattered electron (BSE) image binarization method was used to study the effect of pumping on the composition and pore distribution of the concrete. The effects of the pumping process on the elastic modulus of the paste and interface transition zone (ITZ) were quantitatively evaluated by x-ray diffraction (XRD), back scattered electron energy dispersive spectroscopy (BSE-EDS) and homogenization method, and verified by the test results of nanoindentation. The results showed that the porosity of the paste after the ultra-high-rise pumping decreased by 7.27%, the hydration degree of the cement increased by 6.51%, and the elastic modulus of the paste increased by 3.1 GPa. For the ITZ of the sand, the porosity decreased by 5.3 μm, the average porosity decreased by 15.78%, and the elastic modulus increased by 7.7 GPa. For the ITZ of the gravel, the thickness decreased by 6.91 μm, the average porosity decreased by 16.34%, and the elastic modulus increased by 10.2 GPa. Therefore, the effect of the ultra-high-rise pumping on the ITZ was significantly larger than that of the paste in the concrete. Afterward, the computational method was proposed as the combination of the homogenization method and the Lu and Torquato model. As the result, the elastic modulus of concrete after ultra-high-rise pumping can be precisely predicted on the micro-meso-macro scale due to the promising agreement between the experimental measurements and the numerical results.